Method of improving the safe ironing temperature and crystallinity of cellulose triacetate textile fibres with specific organic media



United States Patent 3,167,385 METHDD 0F IMfROVING THE SAFE IRONING TEMPERATURE AND CRYSTAILLINITY 0F CEL- LULOSE TRIACETATE TEXTILE FERES WITH SPECIFIC ORGANIC MEDIA Ralph James Mann, Maitland Walton Alford, and Boleslaw Krzesinski, all of Spondon, near Derby, England, assignors to British Celanese Limited, a corporation of Great Britain No Drawing. Filed Nov. 29, 1957, Ser. No. 699,515 Claims priority, application Great Britain, Dec. 7, 1956, 37,476/56 3 Claims. (Cl. 8-131) This invention relates to the treatment of textile fibres of cellulose acetate of acetyl value above 59% calculated as acetic acid. Such cellulose acetates are hereinafter referred to as cellulose triacetates.

US. application Ser. No. 467,223, filed November 5, 1954, now US. Patent 3,025,128, discloses that textile materials of fibres of cellulose triacetate as first obtained by melt-spinning, or by a wet or dry spinning process, or by further acetylation of unoriented fibres of cellulose acetate of lower acetyl value, can be improved in very important respects by treating them with an organic liquid which is a swelling agent for the cellulose triacetate. By such treatment the sticking temperature of the material can be increased, likewise the maximum temperature at which the material, particularly when in fabric form, may be safely ironed. The sticking temperature is a measure of the sensitivity of the material to temperature and for the purposes of the above application and the present application is to be taken as the lowest temperature at which a heated iron, left to stand on the fibres or on fabric or other textile material thereof for 10 seconds, sticks to the material. The safe ironing temperature of textile fibres or fabric thereof is closely related to the sticking temperature and in general for practical purposes is lower, for example about lower. The maximum safe ironing temperature of a fabric may be determined by the following methods:

(a) The fabric is laid on a heat-insulating bed of cotton fabric, for example six layers of cotton madapolam laid over a cotton blanket. A heated iron, for example, one of 7 lb. weight having a surface of sixteen sq. in. is placed on the test specimen for 10 seconds. Trials are made each on a fresh portion of the fabric at a series of temperatures each 10 higher than the preceding one and note is made of the lowest temperature at which the material has undergone glazing. The maximum safe ironing temperature is taken as 10 below this temperature; thus if glazing was not perceptible at 170 C. but just perceptible at 180 C. the safe ironing temperature may be taken as 170 C.

(b) This is similar to method (a) except that note is made of the lowest iron temperature which results in stiffening of the fabric; the maximum safe ironing temperature is taken as 20 C. below this temperature. The test is conducted as follows:

An iron weighing 0.6 lb. per sq. inch of sole area is heated to a temperature in excess of 260 C. as conveniently determined by a thermometer immersed in mercury in a hole penetrating to within A" of the iron sole. It is then allowed to cool and as the temperature reaches successively 260 C., 250 0., 240 C., 230 C. and so on it is placed for 10 seconds on the fabric under test which, in turn, rests upon a pad of several layers of dry cotton fabric, e.g., six layers of cotton madapolam laid on a cotton blanket. After allowing to cool in the air for a few minutes, the stiffness of the areas which have been under the iron is compared with that of the surrounding un-ironed area. The safet ironing temperature is taken 3,167,385 Patented Jan. 26, 1965 as 20 C. below the lowest iron temperature resulting in stiffening.

Assessments of safe ironing temperature made by method (b) are substantially the same as those made by method (a). It is considered however that method (b) is more convenient, it being rather easier to decide whether stiffening has occurred than whether glazing has occurred.

Examination of the X-ray diagrams of the cellulose triacetate before and after the treatment prescribed in the above application confirms that the change effected is in general accompanied by rearrangement into a state of greater order of the macromolecules of the cellulose triacetate, or in other words an increase in the proportion of the cellulose triacetate which is in a more or less crystalline state and a decrease in the proportion which is in a so-called amorphous or substantially non-crystalline state. For the purpose of the said prior application it was found convenient to refer to the treated materials as materials of cellulose triacetate of an increased degree of crystallinity. Similarly cellulose triacetate materials as first obtained by melt-spinning or wet or dry spinning processes, or by completely acetlyating unoriented partly acetylated cellulose filamentary materials, were termed materials of cellulose triacetate of a normal degree of crystallinity."

The term textile material is employed in the prior application and in the present application to denote both textile fabrics (and articles made from them) and intermediate structures used in making textile fabrics, such as yarns made up of continuous filaments or spun from staple fibres, and staple fibres themselves in the form of tops, slivers and other structures in which they are more or less loosely bound together. The term fibres includes both continuous filaments of indefinite length and short lengths of filaments such as staple fibres.

The cellulose triacetate fibres and textile materials thereof treated according tothe present application may be those made in the various ways set out in the above application.

The organic liquids specified in the said prior application as suitable for effecting the desired modification of the material, include aqueous acetone of 30-70% strength by weight, lower aliphatic monohydric alcohols (that is alcohols containing not more than 4 carbon atoms in the molecule), and mixtures of said alcohols with acetone, the said mixtures containing 20-70% by weight of acetone.

We have now found certain other organic liquid media which are particularly useful for modifying the properties of cellulose triacetate fibers, particularly in the form of fabrics and other textile materials, in the direction indicated in the said prior application. Not only are these liquid media effective, but some of them present very substantial advantages over the liquids specified in the prior application in respect of ease of employment and especially in that the treatment of the cellulose triacetate materials therewith can readily be carried out in conventional apparatus for liquid treatment of exiles.

Organic liquid media which we have found useful are media comprising the following:

(1) Isopropyl alcohol.

(2) Esters of monohydric aliphatic alcohols of the type ROI-I (R being an aliphatic hydrocarbon radical of preferably up to 3 carbon atoms) with C to C fatty acids, for example such esters of ethyl alcohol, normalor isopropyl alcohol, vinyl alcohol and allyl alcohol. Specific examples of such esters are: methyl acetate, ethyl acetate, normalor iso-propyl acetate, allyl acetate and vinyl acetate.

(3) Acetic acid and propionic acids.

. calcium thiocyanate, with or without a C to C (4) Caprolactam, gamma-butyrolactone or other cyclic lactams or lactones containing a lactam or lactone' ring of up to 6 atoms; urea; amides of C to 0.; fatty acids, e.g., acetamide. or methylacetamide. j I

(5) Mixtures of acetone, water and a water-soluble thiocyanate, e.g., sodium, potassium, ammonium, zinc or fatty alcohol. a

.be paddedwith the liquid media on a padding mangle,

rolled up and allowed to stand. Again a fabricmay be treated with the liquid media on a dye jig, a procedure which is convenient when it is desired to employ temperatures above the ambient temperatures and when the active agentof the liquid media is of low volatility. Thus the (6) Solutions of benzoic acid, salicylic acid or'other benzene carboxylic acids in'C to C fatty alcohols.

(7) Ethylene-methylene-ether.

(8) C to C fatty acid esters, or C to C alkyl ethers (or the corresponding ether-esters) of polyhydric alcohols (including dihydric alcohols), preferably such products as are water-miscible and in particular such as are soluble.

in water to the extent of at least 5 parts in 95 parts of Water by weight at C. The esters, ethers or etheesters may be'those of a polyhydric alcohol containing upto 4, carbon atoms, for example ethylene glycol, glycerol, or diethylene glycol.

Examples of esters which may be employed are glycol monoacetate, glycerol monoacetate', glycerol diacetate,

glycerol triacetate, diethylene glycol 'monoacetate, dis

ethylene glycol diacetate and dipropylene glycol diacetate. Examples of others which may be used are glycol monomethyl ether, glycol mono-ethyl ether, diethylene glycol monoethyl ether and diethylene glycol monobutyl ether.

Again examples of ether-esters arethe acetatepof glycol monoethyl ether glycol monobutyl ether, diethylene glycol monoethyl ether and diethylene glycol monobutyl ether;

Advantageously there is used one ofthe foregoing esters, others or ether-esters of glycol, glycerol or diethylene glycol or other polyhydric alcohol containing up to 4 carbon atoms which either (a) contain a C -C alkyl-ether group and a free hydroxyl group, or (b) contains a C1-C fatty acid ester group and a free hydroxy group, or (0) con- 7 tains a C -C fatty acid ester group and an ether-oxygen.

We particularly contemplate etfecting modification 'of the cellulose triacetate fibres in accordance with 'the'invention byallowin'g the 'said agents in liquid form to-act on the material under such conditions of time, temperature and concentration (with respect to a diluent) that the sticking point or safe'ironing point has been raised by at least 10 C and preferablyuntil the said points are not further raised substantially by continuing the treatment. to isof course that of the substantially dry material after substantially complete removal of the treating agent Removal may be eifected, in the case of water-soluble treating agents, by washing with waterjand drying. Preferably the temperature at which the treatment is effected The'sticking point or safeironing point referred is less than 98 or 100 C. Someof the said organic substances-may be used as such, others are liable to damage the materials but may be used after dilution with.

water or other liquid to such an extent as to yield mixtures which do'not damage the materials unde'r'the'conditions of the treatment. The invention particularly C011, templates the treatment of cellulose triacetate fibres, or

.' fabrics or other textile materials formed, thereof, having a safe ironing pointbelow. 180 or 190 C. so as to raise the safe ironing point by at least '10? C. and preferably by at least 20 C. or more.

Various methods may-be used for effecting the .t reat ment with the organic liquid media. Thus the fibres or textile material may beimmersed in a body of the liquid medium for the required time] Such a procedure may material may be loaded onto one'roll of an enclosed dye jig the trough of which contains the treatment liquid. The material is given oneor more passes through the latter as may be necessary to impregnate the material effectively with the liquid. f Passage and repassage of the material from roll to roll may be continued as long as necessary to effect -the.desired change of the material or the latter maybe left on one ofthe rolls, .preferably with the latter rotating, to the same end. The temperature of the material on the rolls may be maintained by suitably maintain,- ing the temperature of the liquid in the trough. More "particularly when. only a short time of contact between the mater'ial and liquid medium is required the material, for example a fabric, may be given a single passage through a body .of theliquid medium andvimmediately thereafter treated for removal of the liquid medium employed. i

' i It is desirable that in carrying out such treatment the amountof' liquid medium available to the material during the treatment should be substantial, for example at least 150% to 200% by weight based on the dry weight of the material. 7 This will ordinarily be-the case where the treatment is effected with the material immersed in the liquid or where the treatment is effected on a dye jig as described above. a On the other hand, padding methods of supplying a liquid to a textile materialas ordinarily conducted do not leave on the material such high proportions of liquid as those indicated above and must be modified suitably when a'high retention of liquid by the material is; desired. i

The following-are some examples .of specific liquid media which may be employed under the conditions indicated for the purposes of the invention. The cellulose triacetate fabric referred to is of'fibres'of cellulose acetate .of acetylvalueabout 61% calculated as acetic acid and higher by boiling with isopropyl alcoholfor 1 to '2 hours.

Vinyl ace taz e -This may be used undiluted; for example at about20 C. for 30 minutes, at 30C. for 10 min- 7 utes or at 40 'C. for 1 minutet'o raise the safe ironing temperature of a fabric from about 180 C. to 230 C.

. III

(a) 1 Acetic acidr-This may be .used as aqueous solutions of 10-65 strength'by weight,particularly 30-60% strength. At ordinary ternperatu'r'esxthe extent to which the safe ironing temperature can be raised by those solutions appears to be small even withprolonged treatment times,.e.g., 2 hours. Thus the. safe ironing point of a 1 cellulose triacetate fabric may be raised from about 180 be followed in the case of packages of "loose .fibre or rolls of fabric or bobbins of yarn. The'liquid may be quiescent or it may be circulated through the package of material in order to speed up the. process or to obtain greater uniformity of treatment. One method in" the case of textile fabric is to impregnate the latter with a f proportion of the liquid medium which can be retained i by the material, to roll the latter up and to allow it "to stand for the requisite time. Forinstance, the fabric may C. to'200. C. or 210 C. by treatment for 2 hours in a 60% aqueous solution of acetic acid at 20 to 25 C. 'However, by using temperatures of' 70 to C., or at the boil,,a very substantial increase "in safe ironing temperature may be secured in a reasonable time, e.g., 5 to 60 minutes, particularly if the concentration is at least" 20% or better at least 30%. In general the safe ironing temperature of a cellulose triacetate fabric having an initial safe ironing temperature below 190 e.g., about 180 C., can be increased to 220 C. or higher by treatment in aqueous acetic acid of from 20 or 30 to 50 or 60% strength at a temperature between 70 C. and the boil for a sufiicient time. The latter is in general at least 3 minutes but need not as a rule exceed one hour. The following table gives some specific concentrations, temperatures and times, together with the safe ironing temperature attainable.

Time in Safe Concentration of Temperature in ironing acetic acid minutes temperature, o

80 0. up to boiling--- 5 to 10 230-240 80 C 10 230 80 C 10 220 98 30 220230 98 C 30 220 (a) Caprolactam.-This may be used as an aqueous solution of from 25-65% strength by weight, e.g., at 75- 99 or 100 C.; thus a 50% aqueous solution may be used for one hour at 98 C. to raise the safe ironing temperature of a fabric from about 180 C. to about 220 C. Very similar results may be obtained with 40% and 60% solutions under the same conditions. The caprolactam may be removed from the material by washing with water.

(b) Concentrated aqueous solutions of urea, e.g., of 3070% strength, may be used similarly.

(c) Acetamide.--This may be used similarly to caprolactam. Thus the safe ironing temperature of a cellulose triacetate fabric may be raised to 220 C. or higher by treatment for 30 minutes at 80 C. with an aqueous solution of acetamide of 50% strength by weight, followed by washing in water and drying.

(d) Gamma-butyrIactone.-This may be used as an aqueous solution of 200 to 300 cc. per litre at 90 to 98 C.

Aqueous acetone of 40-55% strength by weight containing -15% of water-soluble thiocyanate based on the acetone and Water together. Part of the water may be replaced by a C to 0;, fatty alcohol in which case the maximum percentage of thiocyanate is preferably about 9%. Thus a liquid consisting of aqueous acetone of 50-55% strength by weight containing -12% of ammoniu mthiocyanate based on the acetone and water together may be used, or alternatively, a mixture consisting of 54 parts of acetone, 37 parts of Water of water, 9 parts of a mixture of methyl and ethyl alcohols (in the proportion present in methylated spirit) and 5-7 parts of ammonium thiocyanate. The time of treatment may be from a few seconds to 30 minutes at ordinary temperature.

Solutions of benzot'c acid or salicylic acid in C to C fatty alcohols.These may be used at a concentration of 5 to 25% strength by weight at temperatures of from 60 C. to the boiling point of the solution and for times ranging from 5 to minutes. Thus the safe ironing temperature of a cellulose triacetate fabric may be raised to 220 C. or higher by a 10 minute treatment in a boiling 20% by weight solution of salicylic acid in methylated spirits.

VII

Ethylene-methylene ether.--This may be used as an aqueous solution of 40% to 50% strength by volume at temperatures of 20 to 30 C. Thus the safe ironing temperature of a cellulose triacetate fabric may be raised to around 210 C. by a 10 minute treatment with a 45 to 50% aqueous solution at 30 C. followed by washing with water and drying.

VIII

(a) Diethylene glycol diacetate-This may be used as an aqueous solution of from 3 to 60% strength by weight depending on the temperature and time of treatment. Thus a fabric may be padded with a 60% aqueous solution at 60 C. so that it retains about its own weight of liquid, rolled up and allowed to stand for three hours; after washing with Water and drying the safe ironing point is found to have been raised to about 220 C. Particularly useful however are solutions of from 3 to 35% or 40% strength. Thus a 30 to 35% solution may be used at to 99 C. or boiling temperature for periods of from a few seconds to 15 or 30 minutes. For example the cellulose acetate fabric may be passed through a 30 to 35% aqueous solution at to 99 or 100 C., the time of passage being 5 to 10 or 15 seconds, more specifically a 34% solution may be used at 99 C., the time of passage being about 10 seconds; after washing with water and drying the safe ironing temperature of the material is 220 C. or higher as assessed by method (b) given above. The washing may be effected concurrently with the treatment, the fabric being run first through the diethylene glycol diacetate solution and then directly through the washing water. Finally the fabric is dried on a stenter. Again a 3% to 10% aqueous solution may be used for one to three hours at 95 to 99 C. or 100 C.; for example a 5% solution may be used for 1 /2 to 2 hours, the treatment conveniently being carried out on a dye jig.

Diethylene glycol diacetate is of outstanding value for the purposes of the invention. Aqueous solutions thereof are very effective at concentrations and temperatures which may be varied substantially without on the one hand rendering the solutions ineffective or on the other rendering them liable to damage the material.

(b) Glycerol diacetate (diacetin).-This may be used undiluted. The safe ironing temperature of cellulose triacetate fabric may be raised to 220 C. or higher by a 30 minute treatment at 20 to 30 C. Diacetin may also be used diluted with water in manner similar to those described for diethylene glycol diacetate under (a) above.

(c) Glycerol triacetate (triacetin).This is preferably used in diluted form; thus it may be diluted with an equal volume of benzene and the mixture allowed to act on cellulose triacetate fabric at 20 to 30 C., e.g., for 5 to 10 minutes or more, whereby the safe ironing point may be raised to 220 C. or higher; the material may be freed from triacetin by washing with benzene and drying. Triacetin may also be used diluted with water and, where necessary, suflicient C to C fatty alcohol to yield a homogeneous mixture; thus a treatment liquid may comprise 300 g.p.l. of triacetin and 300 g.p.l. of isopropyl alcohol, the remainder being water.

(d) Ethylene glycol monomethyl or monoethyl ether.-- These may be used undiluted at temperatures up to 50 C. in the case of monomethyl ether and up to 60 C. in the ease of monoethyl ether. By treatment for 30 seconds to 10 minutes at 60 C. with the ethyl ether, or at temperatures up to 50 C. in the case of the methyl ether, the safe ironing temperature of a cellulose triacetate fabric may be raised from 180 to 200 or 210 C.

The treatments of the invention may be carried out while the materials are free to shrink or while shrinkage is partly or wholly restrained. In general freedom to shrink facilitates the raising of the safe ironing point.

1. The method of improving textile fibres of cellulose I triacetate having an acetyl value above about 59%, cal- I culated as acetic acid and initially havinga safe'ironing temperature below 190 C.', which comprises contacting said fibres with at 1east,about"'15,0% their. weight of vinyl acetate for about 1 to 30 minutes at a temperature (it about 40 to 20 C. V 1

2. The method of improving 'textileifibr'es of, cellulose triacetate having an acetyl, value above*about 59%, cal

culated as acetic acid and initially having a safe ironing temperature below 190 C., which comprisescontaeting said fibres with at least about 150% their weight of an,

aqueous solution of acetamide of about"50%, concentration forabout 30 minutes at about 80 -C.-

3. The method of'irnproving' textile fibres of cellulose triacetate having an acetyl value above about 59%, calculated as "acetic acid and initially having a safe ironing temperature below 190 C, which comprises contacting said fibres with at least about 150% their weight of an aqueous solution of about 20-30% by volume of gammabutyrolactone at about 90to 98 C. for a time sufiicient to raise the safe ironing temperature by at least C."

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Wampner May 28, 1940 Sowter Mar. 24, 1942 Schne -V--'----, Sept. 7, 1943' Spence et al. Dec. 7, '1943 Schnegg Apr. 18, 1 944 Baker 1 Nov. 7, 1944 Fin1ays'on" Feb. 18, 1958, Finlayson Dec. 2, 1958 Audas Aug. 25, 1959 Olpin et a1. Feb. 2, 1960 Evans Feb. 23, 1960 Alford'etal, 'Aug. 16, 1960 Salvin et al May 2, 1961 Finlaysonet al Mar. 13, 1962 Finlayson et al. Mar. 13, 1962 FOREIGN PATENTS Great Britain -Sept. 27, 1926 Great Britain' Apr. 11, 1927 i Great Britain Aug. 28, 1930 Great Britain July 15, 1940 Great Britain June 5, 1957 OTHER REFERENCES 7 Baker: Journal of the American Ch'em.- Soc., April 1942, pp.-776-782.

The Handbook of Solvents, Leopold Scheflan at al.,

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509, 608 and 68 -Fortess:' American DyestuifvReporter,Aug. 1, 1955, pp. P524-P537. .7

Plasticizers, D. N. Buttrey, 211ded'.,'1957, pp. 47 and 

1. THE METHOD OF IMPROVING TEXTILE FIBERES OF CELLULOSE TRIACETATE HAVING AN ACETYL VALUE ABOVE ABOUT 59%, CALCULATED AS ACETIC ACID AND INITIALLY HAVING A SAFE IRONING TEMPERATURE BELOW 190*C., WHICH COMPRISES CONTACTING SAID FIBRES WITH AT LEAST ABOUT 150% THEIR WEIGHT OF VINYL ACETATE FOR ABOUT 1 TO 30 MINUTES AT A TEMPERATURE OF ABOUT 40 TO 20*C.
 2. THE METHOD OF IMPROVING TEXTILE FIBRES OF CELLULOSE TRIACETATE HAVING AN ACETYL VALUE ABOVE ABOUT 59%, CALCULATED AS ACETIC ACID AND INITIALLY HAVING A SAFE IRONING TEMPERATURE BELOW 190*C., WHICH COMPRISES CONTACTING SAID FIBRES WITH AT LEAST ABOUT 150% THEIR WEIGHT OF AN AQUEOUS SOLUTION OF ACETAMIDE OF ABOUT 50% CONCENTRATION FOR ABOUT 30 MINUTES AT ABOUT 80*C.
 3. THE METHOD OF IMPROVING TEXTILE FIBRES OF CELLULOSE TRIACETATE HAVING AN ACETYL VALUE ABOVE ABOUT 59%, CALCULATED AS ACETIC ACID AND INITIALLY HAVING A SAFE IRONING TEMPERATURE BELOW 190*C., WHICH COMPRISES CONTACTING SAID FIBRES WITH AT LEAST ABOUT 150% THEIR WEIGHT OF AN AQUEOUS SOLUTION OF ABOUT 20-30% BY VOLUME OF GAMMABUTYROLACTONE AT ABOUT 90 TO 98*C. FOR A TIME SUFFICIENT TO RAISE THE SAFE IRONING TEMPERATURE BY AT LEAST 10*C. 